This invention relates generally to surgical suturing and, in particular, to instrumentation, and methods of using the same, for heat-sealing suture knots.
Wound suturing and vessel ligation are still carried out largely done by hand. A thread attached to a curved needle is guided with forceps from one side of a wound to another, or around a vessel to be occluded. The thread is drawn tight, knotted and cut, and the process is repeated to form multiple stitches. Although the traditional approach is easily accomplished on external wounds, the process is more difficult when applied to internal body cavities, particularly when small incisions are used.
Manually tied sutures present certain problems. For one, surgical knots tied with smooth, thermoplastic materials such as nylon require great care to ensure that the knot does not loosen after closing. For this reason, various tools and techniques have been proposed to enhance knot security, including alternative knot styles and devices that use ultrasonic or thermal energy to join suture material without knots.
One such device is disclosed in U.S. Pat. No. 5,417,700, entitled AUTOMATIC SUTURING AND LIGATING DEVICE. According to this patent, a needle is used to form a passage through tissue, or around a vessel or duct. Suture material is threaded through the passage and secured, whereupon the needle is removed, leaving the thread. In a preferred embodiment, the device comprises two curved, opposed pincer-like needles which penetrate the tissue on either side of the wound, or surround the vessel or duct, with the needles meeting opposite the device. The thread is drawn and secured at a given tension, cut and the ends, and ultrasonically welded, afterwhich the device is removed, leaving a knot-free stitch or ligature.
U.S. Pat. No. 5,565,122 discloses a suture cutter including a housing with an electrical power source and a trigger having open and closed positions. A suture clamp with a stationary jaw and a pivoting jaw and radiant heating element is attached to the distal tip of the device. An actuator connects the trigger to the pivotal jaw and electrical circuitry, such that closing of the trigger holds a strand of suture material between the jaws, after which the strand is severed and cauterized using the radiant heating element.
Although devices of the type just described would appear to successfully cut and weld or coagulate individual suture fibers, they do not consider joining or sealing a partial or completed suture knot. In a growing number of surgical procedures, however, the need to fortify the suture knot itself is becoming more desirable if not necessary. Due to the increase in arthroscopic and laproscopic procedures to reduce incision magnitude and post-operative convalescence, an increasing number of knots must be tied within body cavities and through small openings. This may be technically cumbersome, time consuming, and occasionally ineffective compared to standard open techniques. Ironically, the low coefficient of friction that allows for sliding knots into a body cavity is the bane of knot or loop security.
According to journal articles directed to knot security, a serious pitfall in tying sutures is the formation of a sliding knot. In one experiment, the strength of a chromatic catgut loop fell from 3.23 kp to 0.15 kp when a sliding knot was used. Mersilene, Dexon, polyester, polyethylene, monofil nylon and silk all have significant failures (25 percent of the time) due to knot slippage, even with square knots.
Generally, the more knots that are tied, the more security is obtained. However, it has been reported that in the case of some common suture materials, an absolutely secure knot could not be obtained even with as many as six or seven well snugged-down throws. Teflon and silicone-impregnated sutures in particular exhibit this phenomenon. Indeed, a linear relationship appears to exist between the coefficient of friction with respect to a given suture material and relative knot security. Evidently, the low coefficient of friction that makes it easy to slide knots for arthroscopic-type procedures is also the reason behind low knot security using existing techniques.
The present invention solves problems associated with suture knot security by providing an instrument operative to coagulate and heat-seal suture knots incorporating thermoplastic materials. The instrument takes the form of an elongated tool having a proximal end adapted to gripping by a user, and a distal tip operative to at least partially melt a suture knot. It has been discovered that by heat-sealing the ends of various suture materials, the integrity of the given construct is dramatically increased, often doubling the holding power, thereby increasing the likelihood of a successful surgery.
In the preferred embodiment, a short channel is formed providing a path to the knot-melting region, allowing the tool to function as a knot slider or pusher prior to sealing. The channel may be in the form of a groove, tube or other feature enabling one or more strands of suture material to be dressed away from the tip when heated.
The electrical conductors used to activate the heating element at the tip of the tool may be bipolar or unipolar, in which case the body of the patient is used as the electrical return path. The tool may be entirely self-contained and battery operated, though, in the preferred embodiment, the distal portion of the tool is provided as a removable insert to existing Bovie instruments.